Signaling system



May 12, 1925.

P. B. MURPHY SIGNALING SYSTEM Filed Nov. 10, 1921 Patented May 12, 1925.

UNITED STATES PATENT OFFICE.

PAUL B. MURPHY, 0F NYACK, NEW YORK, ASSIGNOB T0 WESTERN ELECTRIC COI- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

SIGNALING SYSTEM.

Application filed November 10, 1921. scrial'llo. 514,208.

To all whom it may concern:

Be it known that I, PAUL B. Mnnrnr, a citizen of the United States, residing at Nyack, in the county of Rockland, State of New York, have invented certain new and useful Improvements in Signaling Systems, of which the following is a full, clear, concise, and exact description. p

This invention relates to signaling systems and more particularly to a method of and means for signaling over transmission lines;

One of the objects of this invention is to provide improved means for signaling over long transmission lines.

Another object is to provide improved means for signaling over transmission lines designed primarily to efficiently transmit message currents.

Another object is to provide, in a system of this nature, improved means for preventing mutual interference between ringing and message currents.

Another object is to provide for two-way transmission in a system of this nature.

To attain the objects of this invention each end of the transmission line is provided with a sendin and a receiving circuit. The sendin c1rcuit comprises means for producing an transmitting oscillations of a single audible frequency interrupted at a low frequency rate. The receiving1 circuit comprises. means for rectifying an translating the modified oscillations into a signal.

The receiving circuit is also provided with a tuned circuit so as to exclude all audible frequency currents except that current having the frequency selected for signaling purposes- The receiving circuit is further provided with means which responds only to an audible frequency current modulated or interrupted at a predetermined rate, so that the component of speech currents present on the line, during conversation, of the particular frequency selected for slgnahng, will not cause the actuation. of the signahng device. The receiving circuit is also provided with means for preventin voice frequency currents from a acting the receiving circuit at the outgoing station.

It is believed that the invention will be better understood from the following descriptionhaving reference to the accomdenying drawing showing, in diagrammatic outgoing form, a specific embodiment of the invenion.

In the drawing reference character L designates a telephone transmission line extending between stations A and B. The rectangles R and R indicategthat, any well known voice repeating apparatus may be inserted in the hne.- It 1s to be understood that the line L may-be composited or simplexed, but since such arrangements are old and. well known-in the art, it is, not thought advisable to complicate the drawing with such a showing. Stations A and B are eqmpped with like apparatus, the equipment for station B being com letely shown,

and for station A,in part 0 y, in order to avoid unnecessarily complicating the drawin Like apparatus isdesignated with like re erence characters except that at the station A primes are added to the reference characters. Cord circuits G and C are for the purposes of extending connections over the transmission lines and only the apparatus which forms a part of this invention is shown. It will be understood that any suitable cord circuit for the traflic conditions desiredmay be employed embodying the' elements shown. Signals 14,and 14 are actuated in responseto an incoming call for their respective stations.

cmts is shown at station A to illustrate how the station A may call station B, it being understood that the remaining apparatus is a duplicate of that shown at station B. The apparatus shown to the right of and below the dotted line comprises a sending and receiving circuit for station B. The sending circuit includes a source of oscillations 0. While a generator is herein-shown as a source of oscillation s,it will be understood that any other suitable means may be employed.

By means of a; generator 8 and a relay 21, the oscillations are modified in a predetermined manner. In the following description the oscillations will be described Only suflicient I apparatus for the sending and receiving cir-' cludes a tuned circuit, a ,V of the well known type and a chain of relays including relay 29. The tuned circuit includes a eondenser 24 and a coi l 25 and is preferabiy so designedas to exclude all Voice frequency and alternating currents except that current having the frequency selected for signaling. In order'to prevent undue loss to voice currents on the line, the impedance of the cir-' cuit consisting of the line winding of transrespondsto the alternating current which through its left-hand is induced into the secondary of coil 28, due to the rectified groups of modulated audible frequency current flowing through ic'seprimary, to control relays 33, 44 and 45 of the chain of relays, which relays in turn control the application of 16 cyclecurrent from the source '46 which current actuate-s the signalingdevice 14. I v l a It is believed that the invention may be more fully comprehended from the following detailed description of the operation vof' the system.

Assuming that it is desired to signal station B from station A over the transmis sion line L, the operator at station A will insert lug 10 of the link circuit G into the jac 11, whereupon the signaling device. 14' is disconnected from the transmission. line. The operator may then actuate the key K connecting the source 5' of low frequency ringing current to the'line, causing the energizatlon of the relay 60 at the sending station. The path forthe energization of 60' may be traced as follows, from source of ringing current 5', through the upper contacts of key K, tips of pluglfi' and ack 11', coil 49, condenser 47',outer contacts of relay 45 winding of relay 60', in ner contacts of relay 45', coil 48', ringsof jack 11' and lug 10', lower normal contacts of key K to'source of ringing current 5'. Relay 60', in operating, completes, throughits contacts, an obvious circuit for relay 20'- Relay 20, in operating, connects.- contacts, the source of oscillations O to the transmission line. Throu'h the right-hand contacts of relay 20, re ay 21f is connected in circuit wit the source of low frequency ringing current S. The generator Sf generates alter- Hating current of preferably'16 to 20 cycles per second, and each time relay 21' energizes, oscillations from the source 0' will be transmitted over the line L through the repeaters R and R. The characteristics of the transmissionline, containing repeaters I R and R are such that voice frequency'cub i ntseonly are, transmitted efficiently, and

The circuit including thesecondary winch ingot coil 22, condenser 24andcoil 25,; and the primary of repeating coil 26 isp'iefer ably a tuned circuit of relatively lowim; pedan'ce as heretofore stated, Current through the primary winding of coil. 26induces a corresponding current in tl1 e.sec ondary Winding thereof. The second'ar'y as to have an impedance equaling the impedanceof the grid 41 of thejtube .V. The

modified oscillations are rectified by means of the tube V and the rectified current passes through the primary winding of coil 28. Thecondenser 27 serves as a bypass i for the oscillation components of a rectified group well as to tune the high side of the transformer 28 to the 16 cyc es.' Theimwinding of coil 26 is preferably designed so pedanceof the primarywinding of coil 2 8,-

in conjunction with condenser 27, is approximately equal to the impedance of the plate 42 of the tubeV. The rectified current passing through the primary winding of coil 28 induces an alternating current in the Well known manner into the secondary winding of this coil to cause the operation of alternating current relay 29.: Relay 29 is preferably so designed, that its impedance equals the impedance of the secondary ofv coil 28. As relay 29re'ceives the current produced by the. rectifier'V', the armature thereof willrapidly close the upper and lower contacts alternately, each at the rate j of 16 times per second in accordance with rent generator S. a n \Vhen the upper contacts of relay 29 are closed the condenser 32 will ,be charged by the Battery B due to current flowing ox'er the the frequency of the 16 cycle ringing curfollowing path: from positive pole ofbat tery B, resistance 31, winding of relay 33, condenser 32, upper contacts of relay 29 to minus pole of battery 13 Although current I at this time also flows through the resistance element 30 and the upper contacts of relay 29, thereby-setting up a drop of potential across the resistance element 30 which will aid the charging of the condenser 32, the main charge for this condenser is obtained over the circuit just traced. As soon as the upper contacts of relay 29 are opened, a condenser 32 commences to discharge due to its being short circuited over the series path including the winding of relay 33 and resistances 31 and 30. If the condenser 32 is not fully discharged over the short circuit path during the time that the contacts are open, it will be fully discharged when the lower contacts of relay 29 are closed because a charge will be started in the opposite direction which will be completed due to the current flowing from positive pole of .batteryfthidfigh resistance 30, condenser 32, relay 33,lower contacts of relay 29 to minus pole'of battery B. The resistances I and 31 thus start the discharge of the condenser 32 as soon as-the associated upper and lower contacts of relay 29 are opened resulting in the current through relay 33 assumin a wave form that is substantially sinusoidal. This operation continues as long as the modified oscillations are applied to the transmission line. Relay 33.v is thereupon energized and upon energization shortcircuits relay 44 which is normally operated over an obvious circuit including resistance 50, allowing said relay 44 to release. Relay 44, in releasing, completes a circuit for slow-to-operate relay 45. The circuit of the chain of relays including relays 29, 3.3, 44 and 45, is so designed that their operation will not be completed except when the rate of operation of relay 29 is between 16 and 20 cycles. For example, relay 33 is so designed that it must have current of '16 to 20 cycles'in suflicient quantity to hold it operated and if relay 29 is vibrated at a greater or lower rate sufiicient current will not flow through relay 33 to hold it continuously operated. Continuous operation of relay 33 is necessary before relay 44 releases. Relay 45, in operating, connects 16 cycle current from the source 46 to the transmission line to actuate the drop 14.v

This 16 cycle current is excluded from the receiving circuit at station A due to the characteristics of the line L and its associated apparatus which may or may not include the repeaters R and R. It'is excluded from the receiving circuit at station B due to the fact that the receiving circuit thereat is tuned to exclude all currents except that of the signaling frequency or approximately 950 cycles.

As soon as the operator at-station A restores key K to normal, all apparatus ex cept signaling device 14 is restored to normal. The operator at station B noting the signal produced by the device 14, may insert plug 10 into jack 11 and complete the connection in any well known manner. If the operator at station B desires tosignal the operator at station A, key K is actuated to apply current from the source 5 to the line, causing the actuation of relay 60, which in operating actuates relay 20, which in turn causes the modulated oscillations from the source 0 to be connected to the line L. The receiving circuit at station A (not shown) then responds in a manner similar to that heretofore described for station B to cause the operation of signal 14. It will be readily apparent to those skilled in the art that any suitable signaling device (not shown) may be associated with the cord circuit C so that if station B desires to signal. station A, while the plugs 10 and 10 are in their respective jacks, a signaling device (not shown) in the cord circuit C may be actuated to apprise the operator at station A of such a call.

\Vhat is claimed is: l

1; The method of transmitting ringing currents in such a form that they are effectively transmitted by apparatus designed to efliciently transmit speech currents, which comprises interrupting a single speech frequency current at a lower frequency rate and transmitting and rectifying said interrupted current and translating the rectified current into a signal.

2. The method of transmitting ringing currents in a form such that they are effectively transmitted by apparatus designed to efficiently transmit message currents, and of preventing mutual interference of the ringing and message currents, which comprises modifying a single speech frequency current at a lower frequency rate and transmitting and selectively translating into a signal the ringing currents to the exclusion of the message currents.

3. The method of signaling which comprises modifying a single audible frequency current at the rate of another frequency,

transmitting the modified current, rectifying the same, translating the rectified current into an alternating current of a frequency corresponding to the modifying frequency and translating the alternating current into a signal.

4. The method ofsignaling which comprises modifying a single frequency essential in speech at a lower frequency rate, transmitting the modified current, rectifying the modified current, and translating the rectified current into a signal. A

5. In a signaling system, a transmission line, a source of audible frequency current, means for interrupting current from said source at a uniform rate and applying it to said line, a signal, and means including a rectifying device and responsive to saidinterrupted current for actuating said signal.

6. In a signaling system, a transmission line. a source of audible frequency current, means for modifying current from said source at a definite rate and applying'it to said line, a signal and means including de vices responsive to said modified current for rectifying the same, producing an alternatingcurrent from said rectified current, said alternating current having a frequency equal to the rate of modification and for actuating said signal in response to said alternating current.

7. In a signaling system, a transmission line over which voice frequency currents may be eificiently transmitted,- a source of current having a frequency essential in speech, a source of ringing -current,means responsive to said ringing current for'interrupting current from said first mentioned source at the frequency of said ringing current, a signal, and means associated with said transmission line responsive to said interrupted current from said first mentionedsource'to actuate said signal.

8. In a signaling system,'a transmission line over which voice frequency currents may be efficiently transmitted, extending between a sending and a receiving station, a

source of oscillations, means at the sending station for applying oscillations from said source at fixed intervals to the transmission line, a signal, and means at the receiving station responsive to the applied oscillations for actuating said signal. 7

9. A signaling system comprising a transmitting station, a distant station having signal apparatus, a line connecting said stadetermined rateand applyit'to said line, a

signal, and means including a relay responsive to said current only when interrupted at the predetermined rate to actuate said signal.

11. In a signaling system a two-way transmission line designed to 'efi'iciently transmit voice currents, a .source of audible frequency current at each end of said line, means at each end of said line for interrupting current from said source at a fixed rate and applying it to the line, a signal'at each end of the line, means at each end 'of the line responsive to the interrupted current transmitted from the "opposite end to actuatethe signal, and means at each end of the line for preventing outgoing audible fre uency currents from affecting the signal at t e outgoing end.

12. In a signalingsystem, a transmission memos line, a relay, two contacts therefor, anarmature for sa1d relay, asource of osclllations, means for modulatlng sa1d oscillations and applying them to said line to actuate said relay to alternately make said contacts, a condenser, a circuit for charglng, said condenser when sa1d. armature makes either contact and for discharging said condenser when said armature is alternating between its contacts, an electromagnet actua-ted by the charging and discharging of said condenser, and a signal controlled by said electromagnet.

. 13. In a signaling system, a relay having an armature,'two contacts for said armature, means for vibrating said armature, a direct current source connected to said armature,

a resistance connected to each of said conc1rcu1t COIIDOCtlOIlS' whereby sa1d condenser charges each time an armature vibrat ng in response to peri- I odically varying current, contacts between which saidarmature vibrates, a direct current source connected to said armature, a resistance connected to each of said contacts, a circuit completed through said armature and one of said resistances each time said armature vibrates, a condenser charged at each completion of said circuit, a conductive path around said condenser for discharging it, an electromagnet actuated by the charging and discharging of said condenser, and a signal controlled by .said electromagnet.

15. In a signaling system, a source of 05- cillations which are efliciently transmitted by .a speech frequency apparatus, means for interrupting sa1d oscillations at a definite rate, a source of lower frequency ringing current, a line, means including relays for controlling the application of the interruptingmeans to the first mentioned source and for-controlling the application of the resulting signaling current to said line, and means including a key for actuating said relay control means from said second mentioned source. a

16. In a signaling system, a sending station, a receiving station, a line interconnecting said stations, a ringing current source at said sending station, means for applying current from said source to the originating end of said line, means associated with .the originating end of said line and responsive to current from said source for ap lying current of a frequency in the range 0 audibilityto'the terminating end of said line and for modulating the audible frequency current in accordance with the frequency of.

rectifying the modulated current, and means at said receiving station for translating the rectified current into a signal indication.

17 In a signaling system, a sending station, a receiving station, a line interconnecting said stations, a ringing current source at said sending station, means for applying current from said source to the originating end of said line, means associated with the originating end of said line and responsive to current from said source for applying current of a frequency in the range of audibility to the terminating end of said line and for modulating the audible frequency current in accordance with theifrequency of the current from said ringing current source, a circuitat the terminating end of said line tuned to receive the modulated audible fre- 'quenc-y current to the exclusion of all other voice frequency currents, means for rectifying the modulated current, electromagnetic means inductively coupled to said rectifying means adapted to operate in accordance with the frequency of the rectified current, and a slow-operating relay controlled thereby for eflecting a signal indicationrat the receiving station. I

In witness whereof, I hereunto subscribe my name this 4th day of November A. D.,.1921.

PAUL B. MURPHY. 

